A liquid crystal display (LCD) device uses a LCD panel to display images. As shown in FIG. 1, a display panel in the prior art includes a display area and a non-display area. In the display area, there are provided gate lines (GL1-GLn), data lines (DL1-DLn), and a plurality of pixel units in array arrangement defined by GL (Gate Line) and DL (Data Line). Each pixel unit includes a thin film transistor (TFT) and a pixel electrode, the thin film transistor includes a gate (G), a source (S) and a drain (D), wherein the gate G is connected to gate line GL, the source S is connected to the data line DL, and the drain D is connected to the pixel electrode. In the non-display area, there are provided a gate driving circuit 10 and a source driving circuit 11, the gate driving circuit 10 supplies a voltage to gates through the gate lines GL, the source driving circuit 11 supplies a voltage to sources through data lines DL.
The display panel operates as follows: for a thin film transistor for driving pixel unit, that is, a driving thin film transistor, when a voltage applied to the gate G reaches a turn-on voltage (that is, a threshold voltage, which is a critical voltage applied to the gate so that the source and drain of the thin film transistor begins to turn on), the source S and the drain D enter into a turn-on state, a voltage may be obtained from the pixel electrode which is electrically connected to the drain D, and the liquid crystal molecules are deflected due to a electric field generated by the voltage so that display is performed. However, the turn-on voltage of the driving thin film transistor is not constant, but varies with the temperature, and if there is a deviation between the turn-on voltage and a set turn-on voltage of the driving thin film transistor due to changes in temperature, the deviations are different between various temperature areas. In the prior art, as the voltage supplied to the gate from a gate driving circuit is constant, image flicker is likely to occur in the display panel or the display panel may not display normally. Therefore, a temperature compensating device is needed so as to correct the deviations in the turn-on voltage of the driving thin film transistors due to changes in temperature, so as to avoid the image flicker or abnormal display in the display panel.
The temperature compensating device in the prior art includes a detection unit for detecting the temperature of the display panel. The detection unit includes a thermistor. As the resistance of the thermistor varies with the temperature, the temperature of the display panel may be obtained based on the change in resistance of the thermistor. In the prior art, the temperature compensating device is generally provided on an additional control plate which is adjacent to the display panel to detect the temperature of the display panel. As the additional control plate is separated from the display panel, a temperature detected by the detection unit provided on the addition control plate can not reflect the real temperature of the display panel in time. Also, the result of the thermistor is affected by the manufacturing process, thus it is difficult for the temperature compensating device to accurately correct the deviation in turn-on voltage of the thin film transistor due to changes in temperature.